Angulathilda, Gründel & Nützel, 2013

Gründel, Joachim & Nützel, Alexander, 2013, Evolution and classification of Mesozoic mathildoid gastropods, Acta Palaeontologica Polonica 58 (4), pp. 803-826 : 808

Genus Angulathilda nov.

Fig. 3B .

Etymology: From Latin angulatus, angulated; because of the basal angulated edge; the ending − thilda refers to the ending of the related genus Mathilda .

Type species: Carinathilda calloviensis Gründel, 1997 from glacial erratic boulder, Hohendorf / Mecklenburg−Vorpommern, NE Germany; Callovian .

Included species:? Mathilda binaria Hébert and Eudes−Deslongchamps, 1860 sensu Andreae 1887 , Oxfordian; Purpurina (Pseudalaria) guerreri ( Hébert and Eudes−Deslongchamps, 1860) sensu Couffon 1919 ; Teretrina microstriata Schröder, 1995 , Oxfordian; Teretrina tectispira Schrö− der, 1995, Oxfordian; Carinathilda calloviensis Gründel, 1997 , Callovian; Carinathilda sp. , cf. calloviensis Gründel, 1997 , late Bathonian– early Callovian; Carinathilda bathoniensis Gründel, 1999b , early Bathonian; Carinathilda? naricatoidea Kaim, 2004 , Middle Bathonian; Carinathilda saulae Kaim, 2004 , Valanginian; Carinathilda squiresi Kaim, 2004 , Valanginian; Carinathilda sp. sensu Gründel 2005a, Callovian;? Carinathilda procera Gründel, 2006 , late Bathonian; Carinathilda bandeli Kiel, 2006 , Albian; Carinathilda cf. microstriata (Schröder) sensu Kiel 2006 , Albian;? Carinathilda parviruga Kiel, 2006 , Albian.

Diagnosis.—Protoconch medio− to coaxial, smooth or with radial wrinkles; shell moderately broad with two primary spiral ribs and strongly keeled whorl face; whorl face somewhat concave below and above keel; numerous fine axial ribs (or strong growth lines); base slightly to moderately convex; whorls face joins base at distinct angulation with strong spiral rib; micro−ornament of numerous fine spiral threads present.

Remarks.— Mathilda binaria Hébert and Eudes−Deslongchamps, 1860 sensu Andreae (1887) and Carinathilda procera Gründel, 2006 do not show any micro−ornament (in the latter, this could be due to preservation) and are therefore placed only tentatively in Angulathilda . The Cretaceous Carinathilda parviruga Kiel, 2006 has a distinct umbilicus which is not present in other species of this genus. Several species which were described before SEM studies were possible cannot neither be included nor excluded with certainty because the diagnostic relevant presence of a micro−ornament was not tested.

In contrast to Angulathilda , Carinathilda has a strongly convex base which is not demarcated from the whorl face by an edge; moreover the whorl face is slightly convex below the keel in Carinathilda . Erratothilda has three or more primary spiral ribs.

Stratigraphic and geographic range.—Bathonian to Early Cretaceous; Germany,? France, Poland, Russia.

Figures

Fig. 3. Type species and examples for Jurassic genera of the family Mathildididae. A. Carinathilda carinata Gründel, 1997, bore Kłęby (formerly Klemmen) 1/37, Poland, Bathonian; from Gründel (1997: pl. 7: 98). B. Angulathilda calloviensis (Gründel, 1997), erratic boulder from Hohendorf near Wolgast 3/96/3, Germany, Callovian; from Gründel (1997: pl. 7: 98, 101). Whole specimen (B1), detail of the ornament (B2). C. Erratothilda erratica (Gründel, 1990), erratic boulder from Bauer−Wehrland, Germany, Callovian; from Gründel (1997: pl. 7: 104, 105). Whole specimen (C1), detail showing ornament (C2).